The present invention relates to a speed reduction motor, in which a motor and a speed reduction device are connected to one another so as to reduce and output the rotation of the motor through the speed reduction device.
FIG. 3 illustrates a partially-fragmentary plan view showing a conventional speed reduction motor. The conventional speed reduction motor includes a motor 1 and a speed reduction mechanism 11. The motor 1 includes a stator iron core 2 supporting a stator coil 3, a rotor iron core 4 fixed to a rotary shaft 5, a stator frame 6, and a rear bracket 7 fixedly attached to the stator frame 6. The rear bracket 7 supports the rotary shaft 5 at a portion near the rear end of the rotary shaft 5 through a bearing 8. The motor 1 further includes a fan 9 secured to the rear end of the rotary shaft 5 and a fan cover 10 fixedly attached to the rear bracket 7. The speed reduction mechanism 11 includes a gear casing 12 and a rear gear bracket 13 for housing and installing therein gear members. The gear casing 12 has a rear end portion which is opened. The rear gear bracket 13 is fitted to the rear end portion of the gear casing 12 through an O-ring 14 interposed therebetween. The rear gear bracket 13 supports a portion near a front end of the rotary shaft 5 through a bearing 15. The rotary shaft 5 is provided at a front end portion with a first gear 16 which is in the form of a pinion and which has a relatively small diameter. The first gear 16 is meshed with a second gear 17, which has a relatively large diameter and constitutes a part of intermediate gear members. The second gear 17 is secured to a rotary shaft 18 of the intermediate gear members, thereby transmitting the rotational torque of the rotary shaft 5 from the shaft 5 to the shaft 18 while reducing the rotational speed of the shaft 5. The rotary shaft 18 is supported at its front end to the gear casing 12 through a sleeve bearing 19 and at its rear end to the rear gear bracket 13 through another sleeve bearing 20. The rotary shaft 18 is formed with a third gear 21 which is in the form of a pinion and which has a relatively small diameter. The third gear 21 is meshed with an output gear 23 having a relatively large diameter. The output gear 23 is secured to an output power shaft 24, so that the rotational torque of the rotary shaft 18 is transmitted from the rotary shaft 18 to the output shaft 24 while reducing its rotation speed. Thus, the reduced rotation is outputted from the output power shaft 24. The output shaft 24 is supported at its front end to the gear casing 12 through a ball bearing 25 and at its rear end to the rear gear bracket 13 through a sleeve bearing 26. The speed reduction mechanism further includes washers 22 and 27, and oil seal members 28 and 29.
The rear bracket 7 and the stator frame 6 of the motor 1 are connected to the rear gear bracket 13 with through bolts 30.
In the above-mentioned conventional speed reduction motor, the rotation of the rotary shaft 5, which is produced by the motor 1, is reduced by the two-stage speed reduction mechanism and is transmitted to the output shaft 24, so that the rotation of the rotary shaft 5 is output from the output shaft 24 as a low-speed and high-torque rotation.
However, the above-mentioned conventional speed reduction motor is arranged in such a manner that the rear gear bracket 13 is connected to the rear end portion of the gear casing 12, so that it is necessary to machine mechanical connecting surfaces and associated holes for receiving the bearings, with a high accuracy through a large number of machining steps for the centering alignment of the shafts. Further, since the gear casing 12 and the rear gear bracket 13 are to be machined separately, the gear members supported thereto cannot be meshed with each other with a high accuracy, which leads to the generation of noise.